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Earthquake Hazard

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  1. 1. Department of Earth Sciences KFUPM Introduction to Seismology Earthquake Hazard Introduction to Seismology-KFUPM Ali Oncel [email_address] 33° E 60° E 10° N 37°N
  2. 2. Term-Paper Status Deadline: May 3 (Submit) May 10 (Present) Through the e-mail Introduction to Seismology-KFUPM
  3. 3. Mid-Term Exam May 5 Introduction to Seismology-KFUPM
  4. 4. Previous Quiz <ul><li>Explain the physical meaning of above graph? </li></ul><ul><li>What you think might be a reason for observing roll-off at lower (3) and higher (1) magnitudes. </li></ul>Introduction to Seismology-KFUPM Log N
  5. 5. Natural hazards in time Introduction to Seismology-KFUPM Magnitude Log of frequency Magnitude Log of recurrence interval Source
  6. 6. <ul><li>Example: Seismicity of Stable Craton Cores (SCC) </li></ul><ul><li>Earthquake Catalogue Completeness for SCC </li></ul><ul><li>Magnitude Range for SCC </li></ul><ul><li>Magnitude-Frequency Plot for SCC </li></ul><ul><li>Worldwide rates of stable cratonic core seismicity </li></ul><ul><ul><li>African SCC seismicity </li></ul></ul><ul><ul><li>North American SCC seismicity </li></ul></ul><ul><ul><li>South American SCC Seismicity </li></ul></ul><ul><ul><li>Australian SCC Seismicity </li></ul></ul><ul><li>Seismicity of Canadian Stable Craton </li></ul><ul><li>Seismicity of Arabian Stable Craton </li></ul>Previous Lecture Introduction to Seismology-KFUPM
  7. 7. Spatial distribution of hazards Introduction to Seismology-KFUPM Principal earthquake zones and explosive volcanoes ‘ Ring of Fire’ S. E. Asia Caribbean Mount St. Helens 1980 Montserrat 1995-present Toba 73ka Pinatubo 1991 Tambora 1815 Aitapei 1998 Alaska 1964 Northridge 1994 Loma Prieta 1989 Chile 1960 Izmit 1999 Lisbon 1755 Tangshen 1976 Tokyo 1923 Kobe 1995 Tropical cyclone zones Bhuj 2001 Taiwan 1999 Columbia 1999 Venezuela 2000 Hurricane Mitch 1999 Source
  8. 8. Where do earthquakes occur? Introduction to Seismology-KFUPM Alaska 1964 Chile 1960 Tokyo 1923 Kobe 1995 Turkey 1999 Lisbon 1755 The 20 th C top ten California 1989 1994 Gujarat 2001 Kashmir 2005 Sumatra 2004 Source
  9. 9. SEISMIC HAZARD AND RISK Earthquake quantification So far: how big? M L , m b , M s , M w how much damage? I, I o , I MSK, I MM where? WWSSN, local networks, ISC and now: when? earthquake prediction how often? seismic or earthquake hazard Introduction to Seismology-KFUPM
  10. 10. <ul><li>The probability of an earthquake occurring: </li></ul><ul><ul><li>Specifically: the probability of an earthquake of magnitude m occurring or being exceeded </li></ul></ul><ul><li>or </li></ul><ul><ul><li>the probability of ground motion at level x occurring or being exceeded (where x = I, a, v or d) </li></ul></ul>Seismic hazard and Risk <ul><li>Seismic risk </li></ul><ul><ul><li>$ RISK = HAZARD x VULNERABILITY x $ VALUE (Unesco) </li></ul></ul>Introduction to Seismology-KFUPM
  11. 11. IDNDR Office Introduction to Seismology-KFUPM
  12. 12. Earthquakes as a hazard <ul><li>Estimated > 8 million killed in earthquakes during last millennium </li></ul><ul><li>2 million deaths in 20 th century </li></ul><ul><li>1990-99 cost US$215 billion </li></ul><ul><li>Over 40 countries are under threat from major destructive quakes </li></ul><ul><li>Over 100 a year have potential for serious destruction (> M = 6) </li></ul>Source: USGS Introduction to Seismology-KFUPM
  13. 13. Some notable earthquakes in history Source: Hazard Research Center Introduction to Seismology-KFUPM
  14. 14. Recent notable earthquakes Source: Hazard Research Center Introduction to Seismology-KFUPM
  15. 15. Yearly average of worldwide damage from natural disasters in the last three decades (data from Munich R) Introduction to Seismology-KFUPM
  16. 16. Geological hazards in context: loss events worldwide 2000 Windstorm 38% Others 26% Earthquake & volcanic 14% Flood 22% Total 851 Introduction to Seismology-KFUPM Source
  17. 17. Geological hazards in context II: fatalities worldwide 2000 Quake & volcano 4% Total 9,270 Introduction to Seismology-KFUPM Flood 67% Windstorm 15% Other 14% Source
  18. 18. Geological hazards in context III: economic losses worldwide 2000 Flood 53% Quake & volcanic 1% Other 14% Windstorm 32% Total US$ 31 bn Introduction to Seismology-KFUPM Source
  19. 19. Geological hazards in context IV: insured losses worldwide 2000 Windstorm 75% Other 4% Flood 21% Total US$ 8.3 bn Introduction to Seismology-KFUPM Source
  20. 20. WHAT ARE WE TRYING TO ACHIEVE? <ul><li>S cientifically- study seismicity properties of earthquake sequences cumulative coseismic deformation maximum earthquakes </li></ul><ul><li>Socially- mitigate against earthquake losses </li></ul><ul><ul><li>advise land-use planners </li></ul></ul><ul><ul><li>advise decision makers </li></ul></ul><ul><ul><li>advise insurers </li></ul></ul><ul><ul><li>advise earthquake engineers and constructors </li></ul></ul>Introduction to Seismology-KFUPM
  21. 21. <ul><li>In general terms: </li></ul>estimate hazard - forecasting , time distribution zone or macrozone - space distribution microzone - local fluctuations  define design earthquakes select time histories (  seismograms) what is the maximum earthquake? what is the maximum loading during EQ? What is the lifetime of structure? What is design spectra like? what is the maximum credible loading? Introduction to Seismology-KFUPM
  22. 22. Forecasting earthquakes <ul><li>Forecasting is not prediction </li></ul><ul><ul><li>less precise </li></ul></ul><ul><ul><li>based upon analysis of earthquake return periods rather than identification of pre-cursor y signs </li></ul></ul><ul><li>Active faults or fault segments do not rupture in a random manner </li></ul><ul><ul><li>they have characteristic return periods (or at least return period envelopes ) </li></ul></ul><ul><ul><li>these reflect strain accumulation along the fault and the capacity of the fault to resist strain up to a given characteristic point - for that fault or fault segment </li></ul></ul><ul><li>There are complications : </li></ul><ul><ul><li>Rupture will not occur according to a rigid timetable - there is a return period envelope rather than specific date </li></ul></ul><ul><ul><li>Strain may be released by one large quake or a number of smaller ones (e.g. Marmara Sea south of Istanbul) </li></ul></ul><ul><ul><li>this has implications for risk assessment </li></ul></ul>Introduction to Seismology-KFUPM Source
  23. 23. The Seismic Gap concept <ul><li>Defined as an area in an earthquake-prone region where there has been a below average level of seismic energy release </li></ul><ul><li>The 1989 Loma Prieta quake filled a gap that had been aseismic since 1906 </li></ul><ul><li>Other gaps exist in </li></ul><ul><ul><li>Aleutian arc (Alaska) </li></ul></ul><ul><ul><li>south of Istanbul </li></ul></ul><ul><ul><li>Tokyo </li></ul></ul><ul><ul><li>southern California </li></ul></ul>Istanbul seismic gap Introduction to Seismology-KFUPM Source